= Shape-corrected Kurie plot
{title2=$K_C=\sqrt{N(p)/[p^2F(p)C(T)]}$}
If a beta spectrum has nonconstant shape factor $C(T)$, divide by it as well as by the Coulomb and phase-space factors before taking a square root. A leading unique first-forbidden shape contains $p_e^2+p_\nu^2$ in <natural units>, with Coulomb and nuclear corrections. Dividing only by a Coulomb <Fermi function> does not remove that shape. A straight uncorrected line must therefore be treated as an approximation, not an exact consequence of forbidden-transition <selection rules>.
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